Benign prostatic hyperplasia (BPH) ts one of the most common conditions associated with ageing in men. This direct relationship between the ageing process and BPH incidence and prevalence suggests that certain risk factors associated with BPH development increase with the ageing process. We propose that a component of the prostate microenvironment that may 'evolve' during the ageing process and increase the risk for BPH development and progression, namely, the relationship between epithelial and associated fibroblastic cells. To test this possibility, we propose to utilize an in vitro model system developed in our laboratory. The epithelial component of this model comprises N15C6 cells that genotypically and phenotypically resemble primary prostate epithelial cells, and the stromal component consists of fibroblastic cell populations originating from young, middle-aged or elderly cystoprostatectomy patients. Preliminary data utilizing this in vitro model system demonstrates that paracrine interactions with fibroblast cells alter genotypic expression and augment expression of the proliferative phenotype in immortalized epithelial cells. Therefore, this in vitro model system could recapitulate the 'evolution' of paracrine interactions between prostate epithelial cells and associated fibroblastic cells during the ageing process. Based on data acquired from this model, we hypothesize that the composition of proteins secreted by fibroblast cells derived from young, middle-aged and elderly patients may differ in a patient age-dependent manner. If so, we expect that human prostate epithelial cells may respond differentially, both phenotypically and genotypically, to the particular medley of proteins secreted by fibroblast cells derived from young, middle-aged and elderly patients, and vice versa. This work will be accomplished through the completion of three specific aims: Specific Aim 1. Elucidate the influence of an ageing tissue microenvironment on prostatic proliferation. Specific Aim 2. Isolate fibroblast- or epithlelial-secreted factors that augment expression of the proliferative phenotype. Specific Aim 3. Elucidate how genotype drives phenotype in the context of an ageing prostate tissue microenvironment. The results of these studies should define the specific epithelial- and fibroblast-secreted proteins and their downstream effectors that augment expression of the proliferative phenotype in the human prostate.